Multi-factors Analysis Of Avascular Necrosis Of Femoral Head After Operation Of Femoral Neck Fractures

Objective: Avascular necrosis of femoral head is one of the most serious complications of femoral neck fractures. As the number of the aged people and traffic accidents, violence increases, more patients have been diagnosed as avascular necrosis of femoral head that originates from increasing number of femoral neck fracture cases. To find out factors related to avascular necrosis of femoral head through a retrospective study of patients with femoral neck fractures treated with AO cannulated compressed screws.Methods: Two hundred and twelve cases of fresh femoral neck fractures who had been treated in deparment of orthopaedics and traumatology of Beijing Jishuitan hospital among 6 years were analyzed statistically. Avascular necrosis of femoral head was found in 70 cases(33.0%), among them late collapse occurred in 30 cases(14.2%). Sixteen factors of age, sex, amalgamation, cause of trauma, side of fracture, Garden type, time interval from injury to surgery, reduction method(close or open), postoperative complication, the quality of reduction(Garden index and shorten of femoral neck), Harris scores, time interval of bed rest, time interval of weight-bearing, time interval of fracture healing, time interval of inpatient were analyzed statistically with one-way logistic regression. Then, the cluster analysis and logistic multiple regression were carried out to find out risk factors.Results: By one-way logistic regression, factors that might have an impact on avascular necrosis of femoral head were found out. They included age OR=1.62(95%CI 1.28～5.21), Garden type OR=2.24(95%5CI 1.03～2.69), time interval from injury to surgery OR=2.33(95%CI 1.15～3.37), reduction method OR=2.50(95%CI 1.10～5.68), Garden index OR=3.27(95%CI 2.02～5.29), shorten of femoral neck OR=2.10(95%CI 1.64～2.71), Harris scores OR=5.22(95%CI 1.46～18.19), time interval of bed rest OR=3.03(95%CI 1.57～5.86), time interval of weight-bearing OR=6.15(95%CI 1. 89～9.55), time interval of fracture healing OR=1.19(95%CI 1.01～1.23), time interval of inpatient OR=4.34(95%CI 1.29～8.16). Then, by the cluster analysis and logistic multiple regression, the time interval of bed rest, time interval of weight-bearing, time interval of fracture healing and time interval of inpatient were excluded, the others were risk factors impacted on avascular necrosis of femoral head.By one-way logistic regression, factors that might have an impact on late collapse of femoral head were found out. They included age OR=1.70(95%CI 1.05～2.74), Garden type OR=5.02(95%CI 1.47～17.13), time interval from injury to surgery OR=3.04(95%CI 1.45～6.40), Garden index OR=4.11(95%CI 2.08～8.39), shorten of femoral neck OR=1.89(95%CI 1.38～2.55), Harris scores OR=2.97(95%CI 1.42～6.21), time interval of bed rest OR=2.93(95%CI 1. 44～5.93), time interval of weight-bearing OR=3.36(95%CI 1.44～6.55), time interval of fracture healing OR=4.28(95%CI 1.37～13.35), time interval of inpatient OR=3.04(95%CI 1.48～5.18). Then, by the cluster analysis and logistic multiple regression, the time interval of bed rest, time interval of weight-bearing, time interval of fracture healing and time interval of inpatient were excluded, the others were risk factors impacted on late collapse of femoral head.By one-way logistic regression, factors that might have an impact on late collapse from necrosis were found out. They included age OR=2.93(95%CI 1.44～5.95), Garden type OR=2.26(95%CI 1.30～3.92), Garden index OA=2.04(95%CI 1.38～3.11), shorten of femoral neck OR=1.70(95%CI 1.01～2.87), Harris scores OR=2.57(95%CI 1.23～5.37), time interval of weight-bearing OR=1.38(95%CI 1.05～1.80), time interval of fracture healing OR=1.12(95%CI 1.02～1.24), time interval of inpatient OR=1.12(95%CI 1.02～1.24). Then, by the cluster analysis and logistic multiple regression, the time interval of bed rest, time interval of weight-bearing, time interval of fracture healing and time interval of inpatient were excluded, the others were risk factors impacted on late collapse from necrosis.Conclusion: Age and degree of fracture displacement are the most critical factors that influence the avascular necrosis and late collapse of femoral head. The quality of reduction(alignment) markably contributed to the accidence of avascular necrosis and late collapse of femoral head. The principle of emergency operation, anatomical reduction, ragid fixation, and undisturbed blood supply must be followed in surgery of femoral neck fracture. High age will not lead to an increased incidence of avascular necrosis of femoral head.